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Explanation of five values such as CSS position attribute absolute relative

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May 07, 2018 pm 05:59 PM

position

This article mainly introduces the explanation of the five values of CSS position attribute absolute relative. It has a certain reference value. Now I share it with you. Friends in need can refer to it.

Almost all mainstream All browsers support the position attribute (except "inherit", "inherit" does not support all browsers including IE8 and previous versions of IE, and IE9 and IE10 have not been tested). The following is w3school's explanation of the five values of position. What is needed Friends can refer to

Currently, almost all mainstream browsers support the position attribute (except "inherit", "inherit" does not support all browsers including IE8 and previous versions of IE, and IE9 and IE10 have not been tested yet) , the following is w3school's explanation of the five values of position:

CSS position

Absolute and relative are the most commonly used, and fixed is also commonly used (IE6 does not support fixed) .

1. Absolute (absolute positioning)

Absolute is an element that generates visual positioning and is separated from the text flow (that is, it no longer occupies a position in the document). Refer to The upper left corner of the browser is positioned via top, right, bottom, left (TRBL for short). You can select a positioned parent object (the combination of relative and absolute will be discussed below) or the body coordinate origin for positioning, or you can perform hierarchical classification through z-index. When the TRBL value is not set, absolute uses the coordinates of the parent object as the starting point. When the TRBL value is set, the upper left corner of the browser is used as the original point. The specific case is as follows:

Copy code

The code is as follows:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>position:absolute定位</title>
<style type="text/css">
    html,body,p{
                    margin:0;   
                    padding:0;  
                    list-style:none;
    }
    .center{
                margin:30px;
                border:#999999 solid 10px;
                width:400px;
                height:300px;
    }
    .p1{
            width:200px;
            height:200px;
            background:#0099FF;
            /*设定TRBL*/
            position:absolute;
            left:0px;
            top:0px;
    }
    .p2{
            width:400px;
            height:300px;
            font-size:30px;
            font-weight:bold;
            color:#fff;
            background:#FF0000;
    }
</style>
</head>
<body>
    <p class="center">
        <p class="p1"></p>
        <p class="p2">position:absolute定位测试</p>
    </p>
</body>
</html>

The effect of this code is as follows :

CSS position属性

This is the effect after setting TRBL (setting TRBL to the upper left corner of the browser as the origin), when TRBL is not set (TRBL is not set to the parent object The coordinates are the origin), that is, when p1 is changed to the following code

Copy code

The code is as follows:

.p1{
            width:200px;
            height:200px;
            background:#0099FF;
            /*没有设定TRBL*/
            position:absolute;
    }

The effect is as follows:

CSS position属性

2. Relative (relative positioning)

relative means relative. As the name suggests, it means relative to You can move the element to the position where the element itself should appear in the document. You can use TRBL to move the element's position. In fact, the element still occupies its original position in the document, but it is visually moved relative to its original position. The specific case is as follows:

Copy the code

The code is as follows:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>position:relative定位</title>
<style type="text/css">
    html,body,p{
                    margin:0;   
                    padding:0;  
                    list-style:none;
    }
    .center{
                margin:30px;
                border:#999999 solid 10px;
                width:400px;
                height:300px;
                background:#FFFF00;
    }
    .p1{
            width:200px;
            height:150px;
            background:#0099FF;
            position:relative;
            top:-20px;
            left:0px;
    }
    .p2{
            width:400px;
            height:150px;
            font-size:30px;
            font-weight:bold;
            color:#fff;
            background:#FF0000;
    }
</style>
</head>
<body>
    <p class="center">
        <p class="p1"></p>
        <p class="p2">position:relative定位测试</p>
    </p>
</body>
</html>

The effect produced by the code is as follows:

CSS position属性

3. The combination of relative and absolute

Floating is often used to layout the page during web design, but There are many uncertain factors caused by floating (for example: IE browser compatibility issues). Relatively speaking, positioning in some layouts will be simpler, faster, and more compatible (used in combination with relative and absolute). The following is an example in a web page (the head part of the web page). The specific code is as follows ：

Copy code

The code is as follows:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
html,body,p,ul,li,a{
                    margin:0;   
                    padding:0;  
                    list-style:none;
}
a, a:hover{
 color:#000;
 border:0;
 text-decoration:none;
}
    #warp,#head,#main,#foot
{
    width: 962px;
}
/*设置居中*/
#warp{
    margin: 0 auto;
}
#head{
            height:132px;
            position:relative;
}
.logo{
        position:absolute;
        top:17px;
}
.head_pic{
            position:absolute;
            top:17px;
            left:420px;
}
.sc{
            position:absolute;
            right:5px;
            top:12px;
}
.sc a{
            padding-left:20px;
            color:#666;
}
.nav{
        width:960px;
        height:42px;
        line-height:42px;
        position:absolute;
        bottom:0px;
        background:url(img/nav_bj.jpg) no-repeat center;
}
.nav ul{
            float:left;
            padding:0 10px;
}
.nav li{
            float:left;
            background:url(img/li_bj.jpg) no-repeat right center;
            padding-right:40px;
            padding-left:20px;
            text-align:center;
            display:inline;
}
.nav li a{
                font-size:14px;
                font-family:Microsoft YaHei !important;
                white-space:nowrap;
}
.nav li a:hover{
                    color:#FBECB7;
}
</style>
<title></title>
</head>
<body>
    <p id="warp">
        <p id="head">
            <p class="logo"><img  src="/static/imghwm/default1.png"  data-src="img/logo.jpg"  class="lazy"   / alt="Explanation of five values such as CSS position attribute absolute relative" ></p>
            <p class="head_pic"><img  src="/static/imghwm/default1.png"  data-src="img/head_pic.jpg"  class="lazy"   / alt="Explanation of five values such as CSS position attribute absolute relative" ></p>
            <p class="sc">
                <a href=""><img  src="/static/imghwm/default1.png"  data-src="img/sc_btn.jpg"  class="lazy"   / alt="Explanation of five values such as CSS position attribute absolute relative" ></a>
                <a href=""><img  src="/static/imghwm/default1.png"  data-src="img/sy_btn.jpg"  class="lazy"   / alt="Explanation of five values such as CSS position attribute absolute relative" ></a>
                <a href=""><img  src="/static/imghwm/default1.png"  data-src="img/kf_btn.jpg"  class="lazy"   / alt="Explanation of five values such as CSS position attribute absolute relative" ></a>
            </p>
            <p class="nav">
                <ul>
                    <li><a href="">首页</a></li>
                    <li><a href="">关于我们</a></li>
                    <li><a href="">团队文化</a></li>
                    <li><a href="">公司动态</a></li>
                    <li><a href="">资讯参考</a></li>
                    <li><a href="">业务中心</a></li>
                    <li><a href="">合作银行</a></li>
                    <li><a href="">联系我们</a></li>
                </ul>
            </p>
        </p>
        <p id="main"></p>
        <p id="foot"></p>
    </p>
</body>
</html>

The effect is as follows:

CSS position属性

In the above code, the relative positioning is first set for the head. Then you can see that all the sub-elements inside will be positioned relative to the head instead of relative to the body after setting absolute. This is much simpler and more convenient than using floating, and there is no need to worry about compatibility issues.

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